Current Address: Faculty of Environment, University of Waterloo, 200 University Avenue West, Waterloo, ON, Canada N2L 3G1.
Macroturbulent coherent structures in an ice-covered river flow using a pulse-coherent acoustic Doppler profiler
Article first published online: 6 NOV 2012
Copyright © 2012 John Wiley & Sons, Ltd.
Earth Surface Processes and Landforms
Volume 38, Issue 9, pages 937–946, July 2013
How to Cite
Demers, S., Buffin-Bélanger, T. and Roy, A. G. (2013), Macroturbulent coherent structures in an ice-covered river flow using a pulse-coherent acoustic Doppler profiler. Earth Surf. Process. Landforms, 38: 937–946. doi: 10.1002/esp.3334
- Issue published online: 8 JUL 2013
- Article first published online: 6 NOV 2012
- Accepted manuscript online: 24 SEP 2012 09:18PM EST
- Manuscript Accepted: 13 SEP 2012
- Manuscript Revised: 8 SEP 2012
- Manuscript Received: 28 FEB 2012
The aim of this work is to compare macroturbulent coherent structures (MCS) geometry and organization between ice covered and open channel flow conditions. Velocity profiles were obtained using a Pulse-Coherent Acoustic Doppler Profiler in both open channel and ice-covered conditions. The friction imposed by the ice cover results in parabolic shaped velocity profiles. Reynolds stresses in the streamwise (u) and vertical (v) components of the flow show positive values near the channel bed and negative values near the ice cover, with two distinctive boundary layers with specific turbulent signatures. Vertically aligned stripes of coherent flow motions were revealed from statistics applied to space-time matrices of flow velocities. In open channel conditions, the macroturbulent structures extended over the entire depth of the flow whereas they were discontinued and nested close to the boundary walls in ice-covered conditions. The size of MCS is consequently reduced in scale under an ice cover. The average streamwise length scale is reduced from 2.5 to 0.4Y (u) and from 1.5 to 0.4Y (v) where Y is the flow depth. In open channel conditions, the vertical extent of MCS covers the entire flow depth, whereas the vertical extent was in the range 0.58Y–1Y (u) and 0.81Y–1Y (v) in ice-covered conditions. Under an ice cover, each boundary wall generates its own set of MCS that compete with each other in the outer region of the flow, enhancing mixing and promoting the dissipation of coherent structures. Copyright © 2012 John Wiley & Sons, Ltd.